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View Full Version : Window reflections, please help


maikukai
12-07-2005, 06:04 PM
I have this project almost completed and I am pretty happy with the results. My only problem is I am having trouble with the reflections in the windows. I've added a 360 skydome to the environment channel, but you can't really see it. I want reflection but still enough transparency to see inside.

What's the best way to have a 360 environment reflect in the windows of my building?


FYI: My scene is lit with HDRI and one omni with area shadows. The gray background has a compositing tag so it is not seen by GI.

AdamT
12-07-2005, 08:11 PM
I would lower the transparency. First you might want to try a test render with transparency off altogether--make sure the reflections are actually there.

Per-Anders
12-07-2005, 08:13 PM
or you could enable additive in the transparency channel, and then modify your refleciton channel as you need (though just remember that this will also add other channels, like color etc).

maikukai
12-07-2005, 08:35 PM
AdamT: Why more transparent? Will this help the reflections show up more? I could make the glass on the upper half of the floors more transparent, the bottom half of the floors have a solid pannel behind them. (My boss wants green glass, transparent enough to see inside but with a reflection of the surrounding environment.)

I tried turning off the transparency. The reflections are there but they are super blown out. How do I turn the brightness down without making them go away?

mdme_sadie: I enabled additive in the transparency channel but I'm having the same problem as above, super blown out reflections. (Maybe I should clairify, the image I want reflected is in the enviormnet channel, the actual reflection channel is on but set pretty low, like 8%.) Am I going about this the wrong way? I'll post more info on my glass material when I get home...

Per-Anders
12-07-2005, 08:39 PM
you must lower the enviornment channel then. additive adds what's in the other channels on top of the transparency.

JoelOtron
12-07-2005, 09:21 PM
I sometimes add a very slight hint of bump which helps pick to up reflections.
A large scale to the noise, at a strength of 1 or so.

AdamT
12-07-2005, 09:34 PM
I guess I was unclear: you should make the glass *less* transparent! Also, if you're using the environment channel make sure the "Exclusive" box is checked. That'll ensure that your environment isn't added to your reflections (or v.v.). Then, if you do have objects that you want reflected in the windows, turn up your reflection value so it's the same as your environment value.

Now--crucially--make sure your color + transparency + reflection/environment values add up to 100% or less. Example: transparency of 60%, reflection/environment 30%, color 10%. Otherwise your glass will generate more light than it's receiving.

hth

vid2k2
12-07-2005, 10:45 PM
Aside from all the other excellent suggestions:

If the glass is green and you have reflections added .... also make the reflection
color the same green ( or other off shade ) to keep the reflections from blowing out.

HTH

David

Edit: here's a fast example. Green glass and silver refective glass.
Just a sky with environment from the sky preset folder

vid2k2
12-08-2005, 12:29 AM
Edit: here's the same scene with interior transparency and
additional exterior reflection

maikukai
12-08-2005, 07:20 PM
Cool, Thanks for your help. I got the glass looking good but I think I've got bigger problems than my reflective glass material. I think my fundamental understanding of the material system is flawed. For the glass in the rendering above I had color 100%, Transparency 70%, Reflection 8%. I am guessing from my settings that my glass was generating light. When I went with the percentages AdamT suggested I got the results I was looking for but now my lighting looks horrible. Time is running out on my deadline, so I just went with what I had, only making the glass more green.

Let's see if I can deconstruct what went wrong. My scene is lit using HDRI applyed to a sky object. A GI dome for the lighting with a compositing tag so it is only seen by GI. Next, and don't ask me why I did this, I guess I was in a hurry... I dropped in another sky object and applied a simple gray shader that had Generate GI cut back to 50%. (Kind of defeating the purpose of the HDRI I'm thinking) Then I dropped in an Omni light with Area shadows set close to the corner of the building to make the highlights pop on the metal material on the columns. Combined with my super bright glass material I got lighting I was happy with and that didn't take too long to render (1/2 hour at 2048 x 1536). Well anyway, funny huh?

I'm doing things all wrong, but how do I make it right? I know this is off topic, but can someone school me on setting up a nice lighting rig that doesn't take forever to render?

AdamT
12-08-2005, 07:35 PM
I haven't got much time right now, but in a nutshell I would use GI with an infinite light and area shadows, add other lights or a dome for ambient light, and use the HDRI as an environment map only (in environment channel or on a dome with material set to to cast or receive GI).

maikukai
12-08-2005, 07:42 PM
Trust me, I understand about not having much time. Thanks for your help AdamT, that should be enough to get me started...

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